The present invention relates to a polyurethane foam excellent in mechanical properties, a process for producing the same, and a foam forming composition. More particularly, the present invention relates to a polyurethane foam having a structure in which polymer chains formed by an addition-polymerization reaction (hereinafter abbreviated as addition-polymerization chains) and polyurethane chains are cross-linked to each other, which is excellent in mechanical properties such as hardness and dimensional stability in the case of forming a rigid foam, and which has mechanical properties such as reduced compression set in the case of forming a flexible foam.
Polyurethane foams having addition-polymerization chains and polyurethane chains have been disclosed, for example, in Japanese Publication of Unexamined Patent Application (Tokkai) No. HEI 3-244620 (Document 1), and Japanese Publication of Unexamined Patent Application (Tokkai) No. SHO 63-23956 (Document 2).
The Japanese Publication of Unexamined Patent Application (Tokkai) No. HEI 3-244620 (Document 1) discloses an elastic polyurethane foam obtained by reacting a high molecular weight polyol such as a polyoxyalkylene polyol having a hydroxyl value of 5 to 38 with a polyisocyanate compound in the presence of a low viscosity compound having an addition-polymerizable unsaturated group, a catalyst, and a blowing agent. Furthermore, Document 1 discloses that a compound having zero or one, particularly zero functional group capable of reacting with an isocyanate may be used as the low viscosity compound having an addition-polymerizable unsaturated group, and indicates that if a compound having many functional groups is used, it is incorporated in the polyurethane chains and causes undesirable cross-linking.
Japanese Publication of Unexamined Patent Application (Tokkai) No. SHO 63-23956 (Document 2) discloses a polyurethane that is obtained by admixing a mixture of a long-chain polyol and a short-chain diol with an ethylenic unsaturated esterol such as alkyl hydroxy acrylate or alkyl hydroxy methacrylate to prepare a polyol mixture having storage stability, and reacting the polyol mixture with an organic polyisocyanate by a method such as RIM (reaction injection molding). It is also disclosed in the Document 2 that a blowing agent may be included as an optional component in the RIM.
It is a first object of the present invention to provide a polyurethane foam excellent in mechanical properties.
It is another object of the present invention to provide a rigid polyurethane foam excellent in mechanical properties such as hardness and dimensional stability.
It is a further object of the present invention to provide a flexible polyurethane foam which has mechanical properties such as reduced compression set and in which ball rebound is not reduced even when its density is decreased.
It is a still further object of the present invention to obtain a rigid polyurethane foam that has equal dimensional stability and equal or higher mechanical strength as compared to the case of using conventional monochlorotrifluorocarbon (CFC-11), and has good thermal insulation and flame resistance, when producing a rigid polyurethane foam in the presence of at least one blowing agent selected from hydrogen atom-containing halogenated hydrocarbon, water, low boiling point hydrocarbon, and liquefied carbon dioxide gas.
It is a still further object of the present invention to provide a rigid polyurethane foam reinforced with staple fiber having a high bending strength and a high bending modulus.
Other objects of the present invention, which will be apparent from the above and below descriptions, are broadly achieved by the following polyurethane foam:
A polyurethane foam which is obtained by reacting an addition-polymerizable active hydrogen component comprising a compound having an active hydrogen-containing group and an addition-polymerizable functional group or comprising this compound and a compound having at least 2.5 groups (on the average) containing active hydrogen and not having an addition-polymerizable functional group with an organic polyisocyanate in the presence or absence of at least one auxiliary selected from the group consisting of blowing agents and additives to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane, and which has a structure in which the addition-polymerization chains are cross-linked to the polyurethane chains.
As the above-mentioned addition-polymerizable active hydrogen component, an addition-polymerizable active hydrogen component (A) comprising a compound (A1) having at least one group containing active hydrogen (w) and at least one addition-polymerizable functional group (x) or comprising the compound (A1) and a compound (A2) having at least 2.5 groups (w) (on the average) and not having the group (x) may be employed. When using a combination of the compounds (A1) and (A2) in the component (A), the combination is selected from {circle around (1)} to {circle around (3)} below:
{circle around (1)} a compound (A11) having one group (w) as the compound (A1), and a compound with a value of active hydrogen-containing group of at least 40 as the compound (A2);
{circle around (2)} a compound (A12) having at least two groups (w) as the compound (A1), and the compound (A2);
{circle around (3)} the compound (A11), the compound (A12), and the compound (A2).
Hereinafter, a polyurethane foam obtained using an addition-polymerizable active hydrogen component (A) is referred to as a polyurethane foam [1].
Furthermore, the following addition-polymerizable active hydrogen component (Axe2x80x2) also may be used as the above-mentioned addition-polymerizable active hydrogen component.
Addition-polymerizable active hydrogen component (Axe2x80x2): an addition-polymerizable active hydrogen component that comprises the active hydrogen-containing group (w) and an addition-polymerizable functional group (x), and which is selected from (A31), (A32), and (A33) below; wherein the reaction rate constant K1 between the active hydrogen-containing group (w) and an isocyanate group (z) at 120xc2x0 C. is not more than 1 (liter/mol/sec); the polymerization reaction rate constant K2 of the addition-polymerizable functional group (x) is not less than 10 (liter/mol/sec); and K2/K1 is not less than 100.
(A31): an addition-polymerizable active hydrogen compound which has the active hydrogen-containing group (w) and the addition-polymerizable functional group (x), and which may have a cyclic group (y) reactive with the group (w).
(A32): an active hydrogen compound (A321) having at least three groups (w) or having the groups (w) and (y), and an addition-polymerizable compound (A322) having the groups (x) and (y), used in combination.
(A33): the compound (A31), the compound (A321) and/or the compound (A322), used in combination.
Hereinafter, a polyurethane foam obtained using an addition-polymerizable active hydrogen component (Axe2x80x2) is referred to as a polyurethane foam [2].
In the polyurethane foam of the present invention, the addition-polymerizable active hydrogen component (A) comprises at least one compound (A1) having at least one group containing active hydrogen (w) and at least one addition-polymerizable functional group (x), or comprises the compound (A1) and at least one compound (A2) having at least 2.5 groups (w) (on the average) and not having the group (x).
The active hydrogen-containing group (w) in the compound (A1) may be at least one group containing active hydrogen selected from hydroxyl, mercapto, carboxyl, primary amino, and secondary amino groups, etc., and preferably used is a hydroxyl group. Examples of the addition-polymerizable functional group (x) in the compound (A1) include radical-polymerizable functional groups of the terminal olefin type or the internal olefin type, cationic-polymerizable functional groups (e.g. vinyl ether group, propenyl ether group), and anionic-polymerizable functional groups (e.g. vinyl carboxyl group, cyano acryloyl group). Preferable are radical-polymerizable functional groups, and particularly preferable are radical-polymerizable functional groups of terminal olefin type. The compound (A1) usually has from 1 to 10, preferably from 1 to 5 addition-polymerizable functional groups (x), and usually from 1 to 8, preferably from 1 to 5 groups containing active hydrogen (w).
As the compound (A1) preferable is at least one active hydrogen compound having an active hydrogen-containing group (w) and also having a radical-polymerizable functional group of terminal olefin type represented by the general formula (1) below 
wherein R denotes hydrogen, an alkyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 21 carbon atoms.
Particularly, active hydrogen compounds having an acryloyl group or a methacryloyl group are preferably employed as the at least one active hydrogen compound having a radical-polymerizable functional group represented by the general formula (1).
As the compound (A1), more preferably used is a compound represented by the general formula (3) below 
wherein R denotes hydrogen, an alkyl group having 1 to 15 carbon atoms, or an aryl group having 6 to 21 carbon atoms; X denotes O, S, or NH; p and q denote positive integers; Q denotes an active hydrogen-containing group; and Z denotes a residue of an active hydrogen compound from which (p+q)groups containing active hydrogen are removed, respectively. R is preferably hydrogen or an alkyl group, particularly preferably hydrogen or methyl group; and X is preferably O. The value of p is preferably from 1 to 7, more preferably from 1 to 5. The value of q is preferably from 1 to 7, more preferably from 1 to 4. In the case of the flexible foam mentioned below, because the concentrations of the addition-polymerizable functional group and the active hydrogen-containing group are low, elongation or tear strength of the obtained foam may be decreased if q is less than 2. Thus, the value of q is particularly preferably from 2 to 4. Furthermore, the value of (p+q) is preferably from 2 to 8, and in the case of a flexible foam, more preferably it is from 3 to 8. Furthermore, it is preferable to employ hydroxyl group as Q.
Examples of the compounds (A1) include (A1/1) to (A1/4) as follows:
(A1/1): partial esters of unsaturated carboxylic acids with polyols [polyhydric alcohols; polyhydric phenols; polyether polyols in which alkylene oxides (AO) are added to polyhydric alcohols or to polyhydric phenols; polyether polyols in which AO are added to amines; polyester polyols derived from polyhydric alcohols and polycarboxylic acids, and the like]
(A1/2): partially amidated unsaturated carboxylic acids with amines
(A1/3): partial thioesters of unsaturated carboxylic acids with polythiols
(A1/4): vinyl monomers having a hydroxyl group
The polyhydric alcohols among the polyols used in producing the compounds (A1/1) include, for example, dihydric alcohols [ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butylene glycol, neopentyl glycol, and the like], alcohols with a value of 3 to 8 or more [glycerol, trimethylolpropane, pentaerythritol, diglycerol, xcex1-methylglucoside, sorbitol, xylitol, mannitol, glucose, fructose, sucrose, and the like], and combinations of two or more of these.
The polyhydric phenols among the polyols used in producing the compounds (A1/1) include, for example, hydroquinone, bisphenols (bisphenol A, bisphenol F, etc.), formalin low condensation products of phenol compounds (novolac resin, intermediate of resol), and combinations of two or more of these.
The amines in the polyether polyols in which AO are added to amines among the polyols used in producing the compounds (A1/1) include, for example, ammonia; alkanolamines [mono-, di-, or triethanolamine, isopropanolamine, aminoethylethanolamine, and the like]; alkylamines having 1 to 20 carbon atoms [methylamine, ethylamine, n-butylamine, octylamine, and the like]; alkylenediamines having 2 to 6 carbon atoms [ethylenediamine, hexamethylenediamine, and the like]; polyalkylene polyamines having 2 to 6 carbon atoms in the alkylene groups [diethylenetriamine, triethylenetetramine, and the like]; aromatic amines having 6 to 20 carbon atoms [aniline, phenylenediamine, diaminotoluene, xylylenediamine, methylenedianiline, diphenyl ether diamine, and the like]; alicyclic amines having 4 to 15 carbon atoms [isophoronediamine, cyclohexylenediamine, and the like]; heterocyclic amines having 4 to 15 carbon atoms [piperazine, N-aminoethylpiperazine, 1,4-diaminoethylpiperazine, and the like], and combinations of two or more of these.
The alkylene oxides (AO) which are added to polyhydric alcohols, polyhydric phenols, or amines include, for example, ethylene oxide (hereinafter abbreviated as EO), propylene oxide (hereinafter abbreviated as PO), 1,2-, 1,4- or 2,3-butylene oxide, styrene oxide, and the like, and combinations of two or more of these (when using combinations of two or more of these AO, either random addition or block addition may be employed), but it is not limited only to these examples. Among these examples, it is preferable to use those containing PO and/or EO as main components and containing not more than 20 mass % of other alkylene oxides. The addition reaction may be performed by conventional methods.
The polyhydric alcohols used in the polyester polyols among the polyols used in producing the compounds (A1/1) are same as described above. The polycarboxylic acids include aliphatic polycarboxylic acids [succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, and the like], aromatic polycarboxylic acids [phthalic acid or its isomers, trimellitic acid, and the like], ester-forming derivatives of these polycarboxylic acids [acid anhydrides, lower alkyl esters having 1 to 4 carbon atoms in the alkyl groups, and the like], and combinations of two or more of these.
The compounds (A1/1) are obtained by partially esterifying the polyols listed above with unsaturated carboxylic acids. The unsaturated carboxylic acids include, for example, (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, aconitic acid, cinnamic acid, vinylbenzoic acid, and the like, and combinations of two or more of these [the (meth)acrylic acid herein refers to acrylic acid and/or methacrylic acid, and hereinafter also is referred to in the same way]; ester-forming derivatives of these unsaturated carboxylic acids, for example, halides [e.g. (meth)acrylic acid chloride], acid anhydrides [e.g. maleic acid anhydride, itaconic acid anhydride, and citraconic acid anhydride]; and combinations of two or more of these.
Examples of the compounds (A1/1) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate, glycerol mono(meth)acrylate, glycerol di(meth)acrylate, diethylene glycol mono(meth)acrylate, and the like, and combinations of two or more of these.
The compounds (A1/2) are obtained by reacting the above-mentioned unsaturated carboxylic acids with the polyamines or alkanolamines among the above-mentioned amines. Examples include (meth)acrylamido ethyl amine, (meth)acrylamido hexyl amine, and the like, and combinations of two or more of these.
The polythiols used in producing the compounds (A1/3) include, for example, ethanedithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,4-benzenedithiol, 1,2-benzenedithiol, bis(4-mercaptophenyl) sulfide, 4-t-butyl-1,2-benzenedithiol, ethylene glycol dithioglycolate, trimethylolpropanetris(thioglycolate) thiocyanuric acid, di(2-mercaptoethyl) sulfide, di(2-mercaptoethyl) ether, and combinations of two or more of these. The compounds (A1/3) are obtained by reacting these polythiols with the above-mentioned unsaturated carboxylic acids. Examples of the compounds (A1/3) include acryloyl thioethyl mercaptan, acryloyl thiobutyl mercaptan, and the like, and combinations of two or more of these.
Examples of the compounds (A1/4) include p-hydroxylstyrene, (meth)allyl alcohol, cinnamyl alcohol, crotonyl alcohol, adducts of the above-mentioned alkylene oxides (AO) to these compounds, and combinations of two or more of these.
Preferable among these are partial esters of unsaturated carboxylic acids with polyols among the compounds (A1/1), particularly preferably partial esters of unsaturated carboxylic acids with polyhydric alcohols or their AO adducts, most preferably diethylene glycol mono(meth)acrylate, because they have low viscosity and this also lowers the viscosity of a polyurethane-forming composition when used.
Considering its viscosity-reducing effect in a polyurethane-forming composition, the molecular weight of the compound (A1) per an active hydrogen-containing group is preferably from 40 to 2,500. For the rigid foams described below, it is more preferably from 40 to 500, particularly preferably from 45 to 300.
The compound (A2) is at least one compound having at least 2.5 (on the average), preferably 3 to 8 groups containing active hydrogen (w), and not having an addition-polymerizable functional group (x).
If the number of active hydrogen-containing groups is less than 2.5 (on the average), in the case of forming a rigid foam, mechanical properties such as hardness and dimensional stability are reduced, and in the case of forming a flexible foam, compression set increases.
The active hydrogen-containing group (w) in the compound (A2) may be at least one group containing active hydrogen selected from hydroxyl, mercapto, and amino groups.
Suitable examples of the compounds (A2) are those having 3 to 8 active hydrogen-containing groups selected from hydroxyl, mercapto, and amino groups, preferably hydroxyl group. Examples include the above-mentioned polyhydric alcohols, polyhydric phenols, amines [diamines, polyamines, alkanolamines], polyether polyols, polyester polyols, and the like, particularly preferably at least one polyol selected from the group consisting of polyether polyols and polyester polyols.
The polyether polyols may be known polyether polyols commonly used in polyurethane foams, e.g. adducts of the above-mentioned alkylene oxides (AO) to the above-mentioned polyhydric alcohols, polyhydric phenols, polycarboxylic acids, amines, and the like. It is preferable to use those containing PO and/or EO as main components and containing not more than 20 mass % of other alkylene oxides as the AO, particularly preferably PO and/or EO. The polyester polyols may be known polyester polyols commonly used in polyurethane foams, e.g. polyester polyols derived from the above-mentioned polyhydric alcohols or polyhydric phenols and the above-mentioned polycarboxylic acids. Among these compounds (A2) particularly preferable are polyether polyols in which AO is added to polyhydric alcohols. Moreover, the number average molecular weight of the compound (A2) is preferably from 50 to 10,000, particularly preferably from 60 to 8,000.
In the present invention, a vinyl polymer (F) also may be further dispersed in the compound (A2) as needed. The vinyl polymer (F) may be dispersed in the (A2) after it is polymerized, but preferably it is dispersed by polymerizing a vinyl monomer (f) in the (A2) to be stabilized. Examples of the vinyl monomer (f) include acrylonitrile, styrene, vinylidene chloride, alkyl (meth)acrylate, and the like, and preferable are acrylonitrile and styrene. The amount of the (F) is usually from 5 to 50 mass parts, preferably from 15 to 45 mass parts per 100 mass parts of the (A2).
It is preferable that the reaction rate constant K1 between the active hydrogen-containing group (w) in each of the compounds (A1) and (A2) and an isocyanate group (z) in (B) at 120xc2x0 C. is not more than 1 (liter/mol/sec); the polymerization reaction rate constant K2 of the addition-polymerizable functional group (x) in (A1) is not less than 10 (liter/mol/sec); and K2/K1 is not less than 100.
The ratio of the (A1) contained in the component (A) based on the total mass of the compounds (A1) and (A2) is usually from 1 to 100 mass %, more preferably from 2 to 100 mass %. For the rigid foams described below, it is more preferably from 5 to 100 mass %, particularly preferably from 10 to 95 mass %.
An essential component in the component (A) is a compound (A1) or a combination of compounds (A1) and (A2). When a combination is used, it is selected from {circle around (1)} to {circle around (3)} below:
{circle around (1)} a compound (All) having one group containing active hydrogen (w) as the compound (A1), and a compound having a value of active hydrogen-containing group of at least 40 as the compound (A2),
wherein the value of active hydrogen-containing group refers to xe2x80x9c56100/(equivalent of active hydrogen)xe2x80x9d, i.e. xe2x80x9c56100/(molecular weight per an active hydrogen-containing group)xe2x80x9d;
{circle around (2)} a compound (A12) having at least two groups containing active hydrogen (w) as the compound (A1), and the compound (A2);
{circle around (3)} the compound (A11), the compound (A12), and the compound (A2).
That is, when the compound (A2) used in the combination has a value of active hydrogen-containing group of 40 or more, the compound (A1) may be either the compound (A11) having one group containing active hydrogen (w) or the compound (A12) having at least two groups (w). However, when the compound (A2) used in the combination has a value of active hydrogen-containing group of less than 40, it is necessary to use at least partially the compound (A12) having at least two groups containing active hydrogen (w) as the compound (A1). This is because, when the compound (A2) is a long chain compound with a value of active hydrogen-containing group of less than 40, which is considerably low, one group containing active hydrogen (w) that is contained in the compound (A1) is not enough to keep a sufficient degree of cross-linking of the addition-polymerization chains per a length of the polyurethane chains formed. On the other hand, when the compound (A2) has a relatively short chain with a value of active hydrogen-containing group of 40 or more, a sufficient degree of crosslinking of the addition-polymerization chains per a length of the polyurethane chains formed is ensured, even when the compound (A1) has only one group containing active hydrogen (w). Because sufficient crosslinking is ensured, when forming a rigid foam, polyurethane foams excellent in mechanical properties such as hardness and dimensional stability can be obtained, and when forming a flexible foam, polyurethane foams having mechanical properties such as small compression set can be obtained. Also, because of the same reason, when using only the compound (A11) as the (A1) in a combination of the (A1) and (A2), it is preferable to use a compound having a value of active hydrogen-containing group of at least 60, particularly preferably at least 100, as the compound (A2). In each case of the above {circle around (1)} to {circle around (3)}, the amount of the compound (A1) based on the total mass of the compounds (A1) and (A2) is preferably from 1 to 99 mass %, more preferably from 2 to 95 mass %. In the case of {circle around (3)}, the amount of the compound (A12) based on the total mass of the compounds (A11) and (A12) is preferably at least 5 mass %, more preferably at least 20 mass %.
In the present invention, at least one compound (A0) containing an addition-polymerizable functional group and not having an active hydrogen-containing group also can be used in the component (A) as needed. As the addition-polymerizable functional group in the (A0), the same groups as in the compound (A1) may be employed, and preferable are radical-polymerizable functional groups. Examples of the radical-polymerizable functional groups include acryloyl, methacryloyl, vinyl, vinylbenzyl, vinylphenyl, and allyl ether groups, and the like. A preferable radical-polymerizable functional group is an acryloyl or methacryloyl group.
The number of the addition-polymerizable functional groups in the compound (A0) is usually from 1 to 10, preferably from 1 to 8. When increase of the mechanical strength is significant, the number of the addition-polymerizable functional groups in the (A0) is preferably from 2 to 8, particularly preferably from 4 to 8. Considering to lower the viscosity of the polyurethane-forming composition, the viscosity of the compound (A0) is preferably not more than 1,000 mPaxc2x7s (at 25xc2x0 C.), particularly preferably not more than 500 mPaxc2x7s (at 25xc2x0 C.). Furthermore, the (A0) also may be contained in the component (A) along with the (A1) as a by-product which is simultaneously formed when producing the (A1). The amount of the (A0) is usually not more than 80 mass %, preferably not more than 60 mass %, particularly preferably not more than 40 mass % based on the total mass of the (A1) and (A0).
As the compound (A0), aromatic hydrocarbon monomers [styrene, xcex1-methyl styrene, etc.], unsaturated nitriles [(meth)acrylonitrile etc.], and the like may be employed, but preferable examples of the (A0) are the (A01) to (A03) as follows:
(A01) esters of unsaturated carboxylic acids with polyols [polyhydric alcohols; polyhydric phenols; polyether polyols in which alkylene oxides (AO) are added to these compounds; polyether polyols in which AO are added to amines; polyester polyols derived from polyhydric alcohols and polycarboxylic acids; and the like]
(A02) amidated unsaturated carboxylic acids with amines
(A03) thioesters of unsaturated carboxylic acids with polythiols
The compound (A01) is obtained by reacting the polyols and unsaturated carboxylic acids used in producing the above-mentioned compound (A11) in a molar ratio different from that in the (A11). The compound (A02) is obtained by reacting the polyamines or alkanolamines and the unsaturated carboxylic acids used in producing the above-mentioned compound (A12) in a molar ratio different from that in the (A12). The compound (A03) is obtained by reacting the polythiols and the unsaturated carboxylic acids used in producing the above-mentioned compound (A13) in a molar ratio different from that in the (A13).
The polyurethane foam [1] of the present invention is obtained by reacting the component (A) with an organic polyisocyanate (B) in the presence or absence of at least one auxiliary (C) selected from the group consisting of blowing agents (C1) and additives (C2) to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane.
In the present invention, it is understood that to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane means that the polymerization of the addition-polymerizable functional group and the polyurethane-forming reaction are carried out simultaneously at least partially during the reaction period. In order to improve the mechanical properties of the polyurethane with increased crosslinking density, it is preferable that the other reaction is initiated before a resin is formed through a curing in one reaction, so that the two reactions are carried out simultaneously.
As the organic polyisocyanate (B), conventional materials used in producing polyurethane foams may be employed. Examples of such isocyanates include aromatic polyisocyanates (B1), aliphatic polyisocyanates (B2), alicyclic polyisocyanates (B3), araliphatic polyisocyanates (B4), modified polyisocyanates (B5), and mixtures of two or more of these.
The aromatic polyisocyanates (B1) include aromatic diisocyanates having 6 to 16 carbon atoms (not including the carbon atoms in the NCO group; this also applies to the isocyanates mentioned below), aromatic triisocyanates having 6 to 20 carbon atoms, crude materials of these isocyanates, and the like. Examples of (B1) are 1,3- and 1,4-phenylene diisocyanates, 2,4- and 2,6-tolylene diisocyanates (TDI), crude TDI, 2,4xe2x80x2- and 4,4xe2x80x2-diphenylmethane diisocyanates (MDI), crude MDI, polymethylene polyphenyl isocyanate (polymeric MDI), naphthylene-1,5-diisocyanate, triphenylmethane-4,4xe2x80x2,4xe2x80x3-triisocyanate, and the like.
The aliphatic polyisocyanates (B2) include aliphatic diisocyanates having 6 to 10 carbon atoms and the like. Examples of (B2) are 1,6-hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like.
The alicyclic polyisocyanates (B3) include alicyclic diisocyanates having 6 to 16 carbon atoms and the like. Examples of (B3) are isophorone diisocyanate (IPDI), 4,4xe2x80x2-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate, and the like.
The araliphatic polyisocyanates (B4) include araliphatic diisocyanates having 8 to 12 carbon atoms and the like. Examples of (B4) are xylylene diisocyanate, xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetramethylxylylene diisocyanate, and the like.
The modified polyisocyanates (B5) include modified materials of the (B1) to (B4) (carbodiimide modified materials, allophanate modified materials, urea modified materials, biuret modified materials, isocyanurate modified materials, oxazolidone modified materials, and the like). Examples of (B5) are urethane modified MDI, carbodiimide modified MDI, urethane modified TDI, biuret modified HDI, isocyanurate modified IPDI, and the like.
Among these listed as the organic polyisocyanates (B), preferable are at least one organic polyisocyanate selected from TDI, MDI, crude TDI, crude MDI, urethane modified TDI, urethane modified MDI, and carbodiimide modified MDI.
The blowing agents (C1) as optional components may be at least one selected from hydrogen atom-containing halogenated hydrocarbons, water, low boiling point hydrocarbons, and liquefied carbon dioxide gas. These are used when foaming with blowing agents.
Examples of the hydrogen atom-containing halogenated hydrocarbons include HCFC types (hydrochlorofluorocarbon types) (e.g. HCFC-123, HCFC-141b, HCFC-22, and HCFC-142b), HFC types (hydrofluorocarbon types) (e.g. HFC-134a, HFC-152a, HFC-356mff, HFC-236ea, HFC-245ca, HFC-245fa, and HFC-365mcf), and the like. Among these, preferable are HCFC-141b, HFC-134a, HFC-356mff, HFC-236ea, HFC-245ca, HFC-245fa, and HFC-365mcf, and combinations of two or more of these.
The low boiling point hydrocarbons usually have a boiling point of xe2x88x925 to 70xc2x0 C., and examples include butane, pentane, cyclopentane, and mixtures thereof. When a usual rigid urethane foam is formed by a foaming method with a blowing agent, the compound (A2) is used as a polyol component. However, because the solubility of the low boiling point hydrocarbons to the compound (A2) is low, if the low boiling hydrocarbons are used as blowing agents, problems may result. For example, the expansion ratio of the obtained foam may be decreased, or the cells easily become non-uniform. On the other hand, in the present invention, a polyurethane foam is formed using the component (A), and the solubility of the low boiling point hydrocarbons to the component (A) is increased by using the compound (A1) as an essential component. Therefore, when the low boiling point hydrocarbons are used as the blowing agents (C1) in producing the foam [1] of the present invention, they can be used in large amounts because of their high solubility to the component (A), and moreover, the premix of the component (A) and the blowing agents has good stability. Therefore, it is free of problems such as that the expansion ratio of the foam may be decreased or non-uniform cells are easily formed, and thus is beneficial. When using a hydrogen atom-containing halogenated hydrocarbon compound as the blowing agent in producing the foam [1] of the present invention, the amount used is usually not more than 50 mass parts, preferably from 5 to 45 mass parts per 100 mass parts of the component (A). When using a low boiling point hydrocarbon as the blowing agent in producing the foam [1] of the present invention, the amount used is usually not more than 45 mass parts, preferably from 5 to 40 mass parts per 100 mass parts of the component (A). When using liquefied carbon dioxide gas as the blowing agent in producing the foam [1] of the present invention, the amount used is usually not more than 30 mass parts, preferably from 2 to 25 mass parts per 100 mass parts of the component (A). When using a combination of a hydrogen atom-containing halogenated hydrocarbon compound and water as the blowing agent in producing the foam [1] of the present invention, the amount of the hydrogen atom-containing halogenated hydrocarbon compound used is usually not more than 45 mass parts, preferably from 5 to 40 mass parts per 100 mass parts of the component (A), and the amount of the water used is usually not more than 10 mass parts, preferably from 0.5 to 8 mass parts per 100 mass parts of the component (A). When using a combination of a low boiling point hydrocarbon and water as the blowing agent in producing the foam [1] of the present invention, the amount of the low boiling point hydrocarbon used is usually not more than 40 mass parts, preferably from 2 to 35 mass parts per 100 mass parts of the component (A), and the amount of the water used is usually not more than 10 mass parts, preferably from 0.5 to 8 mass parts per 100 mass parts of the component (A). When using a combination of liquefied carbon dioxide gas and water as the blowing agent in producing the foam [1] of the present invention, the amount of the liquefied carbon dioxide gas used is usually not more than 25 mass parts, preferably from 0.1 to 20 mass parts per 100 mass parts of the component (A), and the amount of the water used is usually not more than 10 mass parts, preferably from 0.5 to 8 mass parts per 100 mass parts of the component (A). When using water alone as the blowing agent in producing the foam [1] of the present invention, the amount of the water used is usually from 0.1 to 30 mass parts, preferably from 1 to 20 mass parts per 100 mass parts of the component (A).
Examples of the additives (C2) as optional components are foam stabilizers (C21), urethanation catalysts (C22), inorganic powders (C23), hollow microspheres (C24), dehydrating agents (C25), staple fibers (C26), radical-polymerization initiators (C27), chain transfer agents (C28), dust-scattering reducers (C29), and the like. The use of these additives is at least partially different depending on the respective embodiments of foams blown with blowing agents, mechanical froth foam, and syntactic foam as described below. Other examples of the additives (C2) as optional components are polymerization inhibitors, organic lubricants (e.g. calcium stearate, ethylenediamine stearyl amide, oleic acid monoethanol amide, etc.), plasticizers (e.g. dioctyl phthalate, dioctyl adipate, etc.), thixotropy adding agents (e.g. particulate silica), ultraviolet ray absorbing agents, age resistants, antioxidants, colorants (dyes, pigments), flame retardants, antifungal agents, antibacterial agents, and the like.
The foam stabilizers (C21) may be any materials used in usual production of polyurethane foams, e.g. dimethyl siloxane-based foam stabilizer, polyether modified dimethyl siloxane-based foam stabilizer, phenyl methyl siloxane-based foam stabilizer, and the like. Examples of the foam stabilizers (C21) include xe2x80x9cSH-193xe2x80x9d and xe2x80x9cSH-195xe2x80x9d (produced by TORAY DOW CORNING SILICONE CO., Ltd.), xe2x80x9cSZ-1627xe2x80x9d, xe2x80x9cSZ-1931xe2x80x9d, xe2x80x9cSZ-1923xe2x80x9d, and xe2x80x9cSZ-1932xe2x80x9d (produced by NIPPON UNICAR COMPANY LTD.xe2x80x9d, and the like. Among these preferable are xe2x80x9cSZ-1931xe2x80x9d, xe2x80x9cSZ-1923xe2x80x9d, and xe2x80x9cSZ-1932xe2x80x9d. The amount of the foam stabilizer (C21) as an optional component is usually not more than 3%, preferably from 0.1 to 3%, particularly preferably from 0.2 to 2%, based on the total mass of the polyurethane foam-forming composition. For example, in the case of a mechanical froth foam, when using not less than 0.1% of a foam stabilizer (C21), the effects of finely dispersing and maintaining an inert gas, which is blown in during the production of the foam, is improved, so that a molded product with desired density and cell size is easily obtained. When using not more than 3% of a foam stabilizer (C21), bleed-out of the foam stabilizer onto the surface of the molded product is unlikely to occur.
Examples of the urethanation catalysts (C22) include amine-based catalysts (e.g. triethylenediamine, N-ethylmorpholine, diethylethanolamine, bis(dimethylaminoethyl) ether, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexamethylenediamine, 1-isobutyl-2-methylimidazole, 1,8-diazabicyclo-[5,4,0]-undecene-7, etc.), metal catalysts (e.g. stannous octylate, stannic dibutyl dilaurate, lead octylate, etc.), and the like. Preferable among these are triethylenediamine, bis(dimethylaminoethyl) ether, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexamethylenediamine, and stannic dibutyl dilaurate.
The amount of the urethanation catalyst (C22) as an optional component is usually not more than 5%, preferably from 0.001 to 3.5%, particularly preferably from 0.01 to 3% based on the total mass of the polyurethane foam-forming composition. When the amount of the catalyst is not less than 0.001%, the speed of the curing rises, and also the size of the cells in the molded product does not become large, and the texture of the molded product does not become coarse. The foam tends to have a finer texture as the amount of the catalyst increases. However, if the amount of the catalyst exceeds 5%, the speed of the curing may become too fast, and thus problems may be caused in the production of the foam.
The inorganic powders (C23) are used to increase the dimensional stability or mechanical strength of the molded product, or to provide flame resistance. The average particle size of the inorganic powder is preferably not more than 50 xcexcm, particularly preferably not more than 10 xcexcm when it is intended to improve the dimensional stability or mechanical strength. Examples of the inorganic powders (C23) include calcium carbonate, silica, kaoline, talc, aluminum hydroxide, calcium sulfate, barium sulfate, zinc white, titanium oxide, crushed stone, alumina, mica, fly ash, bentonite, ceramic powder, milled fiber, and the like. Preferable among these are calcium carbonate, aluminum hydroxide, silica, and talc.
Because the hollow microspheres (C24) have a cavity inside, they serve as a factor of forming foam layers, and also are used to lighten the weight and improve the processability of the molded product. Examples of such hollow microspheres (C24) include hollow microspheres comprising thermoplastic resins such as polyvinylidene chloride, polymethyl methacrylate, and polyacrylonitrile, hollow microspheres comprising thermosetting resins such as phenol resin, epoxy resin, and urea resin, microspheres comprising inorganic materials such as glass, alumina, shirasu, and carbon. Preferable among these are hollow microspheres comprising thermoplastic resins or thermosetting resins in view of their processability. The diameters of the hollow microspheres (C24) are usually from 10 to 200 xcexcm on the average, and the bulk density is usually from 0.01 to 0.5. Examples of the hollow microspheres (C24) include xe2x80x9cMatsumoto Microsphere F-80EDxe2x80x9d and xe2x80x9cMFLxe2x80x9d series (produced by MATSUMOTO YUSHI-SEIYAKU CO., Ltd.xe2x80x9d, xe2x80x9cphenolic microballoon BJO-0930xe2x80x9d (produced by UNION CARBIDE), xe2x80x9cGlass Bubbles K-15xe2x80x9d and xe2x80x9cGlass Bubbles K-37xe2x80x9d (produced by Scotchlite), and the like.
The dehydrating agents (C25) are used when forming a mechanical froth foam or syntactic foam. They are used to prevent water or moisture from being mixed in the foam-forming composition and acting as a blowing agent in the urethanation reaction, so that a fine surface may be provided when the obtained molded product is processed by cutting. As the dehydrating agents (C25), common compounds having dehydrating effect may be used, but preferable are dehydrating agents which are neutral or alkaline and have a particle diameter of 0.1 to 50 xcexcm. Examples of suitable dehydrating agents (C25) include calcium oxide, calcium sulfate (hemihydrate gypsum), calcium chloride, molecular sieve, and the like. Preferable among these are calcium sulfate (hemihydrate gypsum) and molecular sieve.
As the staple fibers (C26), conventional materials used for reinforcing thermosetting resins may be employed. The staple fibers (C26) have effects, for example, of improving the dimensional stability, bending strength, and bending modulus of the molded product. Furthermore, inorganic materials as the (C26) provide flame resistance. Examples of the materials of the staple fibers (C26) include fiber materials, for example, inorganic staple fibers (C261) such as glass fiber, ceramic fiber, carbon fiber, and rock wool; natural fibers; and synthetic fibers. Among these preferable is glass fiber in view of its effectiveness in reinforcing resins. The thickness of the staple fibers (C26) is preferably from 1 to 10,000 denier, particularly preferably from 10 to 2,000 denier. The length of the staple fibers (C26) is preferably from 0.1 to 50 mm, particularly preferably from 0.5 to 20 mm.
When compounds having a radical-polymerizable functional group are used as the compound (A1) and as needed as the compound (A0) to form the foam [1] of the present invention, these compounds can be brought into reaction in the presence of a radical-polymerization initiator (C27) as needed. Examples of the radical-polymerization initiator (C27) include common radical-polymerization initiators, for example, oil-soluble radical-polymerization initiators such as azo compounds [e.g. 2,2xe2x80x2-azobisisobutyronitrile, 2,2xe2x80x2-azobis-(2,4-dimethylvaleronitrile), 1,1xe2x80x2-azobis-(1-acetoxy-1-phenylethane), etc.], peroxides [e.g. dibenzoyl peroxide, benzoyl peroxide, dicumyl peroxide, t-butyl peroxy benzoate, etc.], and combinations of peroxides and dimethylaniline (redox catalysts), and water-soluble radical-polymerization initiators such as azobiscyano valeric acid, azobisamidinopropane salt, potassium persulfate, and combinations of sodium persulfate and sodium bisulfite (redox catalysts). Preferable among these are oil-soluble radical-polymerization initiators. The amount of the radical-polymerization initiator (C27) is preferably from 0.0001 to 10 mass parts, more preferably from 0.0005 to 1 mass parts per 100 mass parts of the total amount of the (A1) and the (A0) used as needed.
Furthermore, in the case of radical polymerization, a chain transfer agent (C28) may be used as needed. Examples of the (C28) include alkyl mercaptans (e.g. dodecyl mercaptan, mercaptoethanol, etc.), enol ethers described in Japanese Publication of Unexamined Patent Application (Tokkai) No. SHO 55-31880, and the like. Preferable among these are alkyl mercaptans. The amount of the chain transfer agent (C28) is preferably from 0.0001 to 10 mass parts, more preferably from 0.0005 to 1 mass parts per 100 mass parts of the total amount of the (A1) and the (A0) used as needed.
In the case of a rigid polyurethane foam that is processed by cutting, a dust-scattering reducer (C29) may be added as needed. Because a dust-scattering reducer (C29) contained in the foam inhibits the scattering in the air of dust generated when the foam is cut, it is preferable that the foam contains the (C29) when its density is low. Examples of the dust-scattering reducer (C29) include esterified materials and etherified materials in which the hydroxyl groups at both ends of a polyalkylene glycol are enclosed by a fatty acid or a higher alcohol. Examples of the polyalkylene glycols are homopolymers of EO or PO, and block or random copolymers comprising EO and PO. Preferable among these are homopolymer of EO and block copolymers comprising EO and PO. The molecular weight of the polyalkylene glycol is: in the case of polyethylene glycol (hereinafter abbreviated as PEG), usually from 200 to 1000, preferably from 200 to 600; in the case of polypropylene glycol (hereinafter abbreviated as PPG), usually from 200 to 4000, preferably from 200 to 1000; and in the case of a copolymer comprising EO and PO (hereinafter abbreviated as PEPG), usually from 400 to 5000, preferably from 1000 to 3000. Examples of the above-mentioned fatty acids include saturated or unsaturated fatty acids having 8 to 18 carbon atoms. Examples of the saturated fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and the like. Examples of the unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, and the like. Preferable among these are lauric acid and oleic acid. Examples of the above-mentioned higher alcohol are saturated or unsaturated alcohols having 8 to 18 carbon atoms. Examples of the saturated alcohols include lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and the like. Examples of the unsaturated alcohols include oleyl alcohol and the like. Preferable among these are lauryl alcohol, stearyl alcohol, and oleyl alcohol. The dust-scattering reducers (C29) may be used either alone or in combination of two or more types. The (C29) may be a solid form, but it is desirable to be either a liquid or paste form at 20xc2x0 C., so that its effect of inhibiting dust-scattering may be increased. A combination of two or more types of the dust-scattering reducers (C29), in which at least one in the combination is a liquid or paste form also may be employed. Among these dust-scattering reducers (C29) particularly preferable are dilauric acid ester and dioleic acid ester of PEG (molecular weight of 200 to 600).
One embodiment of the polyurethane foam [1] of the present invention is a rigid polyurethane foam [I] in which the component (A) satisfies the requirement that the M value expressed by the formula (2) below is not more than 500
M=J/(K+Lxc3x972xe2x88x922)xe2x80x83xe2x80x83(2) 
wherein J denotes the (number average) molecular weight of the component (A); K denotes the (average) number of the active hydrogen-containing group per molecule of the (A); and L denotes the (average) number of the addition-polymerizable functional group per molecule of the (A).
The M value of the (A) used in the foam [I] is preferably not more than 300, more preferably not more than 250, particularly preferably from 50 to 200. If the M value exceeds 500, the mechanical strength becomes low as a rigid foam.
As the compound (A2) that is used in the rigid polyurethane foam [I] as needed, those comprising at least one selected from polyether polyols, polyester polyols, polyhydric alcohols, and amines [e.g. diamines, polyamines, and alkanolamines] are preferably used. The value (on the average) of the active hydrogen-containing groups (hydroxyl value in the case of polyols) in the compound (A2) used in the foam [I] is preferably from 200 to 1000, more preferably from 250 to 700, particularly preferably from 300 to 650. In the case of the foam [I], when the value (on the average) of the active hydrogen-containing groups in the compound (A2) is not less than 200, the heat resistance and the strength of the obtained foam becomes high. When the value is not more than 1000, the molded product does not become too hard and brittle, and also scorch due to reaction heat may not be generated in the foam.
Furthermore, one embodiment of the rigid polyurethane foam [I] is a rigid polyurethane foam [Ia] having a density of 5 to 900 kg/m3, which is formed using as auxiliaries (C) a blowing agent (C1) and as needed a foam stabilizer (C21) and/or an urethanation catalyst (C22) as additives (C2). The density of the foam [Ia] is preferably from 10 to 500 kg/m3, particularly preferably from 20 to 200 kg/m3.
By further using an inorganic powder (C23) and/or an inorganic staple fiber (C261) as additives (C2) in the foam [Ia], a flame-resistant rigid polyurethane foam can be obtained. The amount of the (C23) and/or the (C261) used to provide the foam with flame resistance is preferably from 9 to 40%, particularly preferably from 20 to 35% based on the total mass of the foam-forming composition. When the amount of the (C23) and/or the (C261) is not less than 9%, flame resistance is improved. When the amount is not more than 40%, the mechanical strength of the foam is not decreased.
Another embodiment of the foam [I] is a rigid polyurethane foam [Ib] which obtained by carrying out a polyurethane-forming reaction by a mechanical froth method without using as auxiliaries (C) a blowing agent (C1) but using inorganic powder (C23) and/or hollow microsphere (C24), a dehydrating agent (C25), and as needed a foam stabilizer (C21) and/or an urethanation catalyst (C22) as additives (C2).
In the mechanical froth foaming method, the inorganic powder (C23) and/or hollow microsphere (C24) serve as nucleating agents when an inert gas is made into fine bubbles and dispersed in the polyurethane foam-forming composition by mechanical stirring, and play a role in keeping the bubbles stabilized. The density of the foam [Ib] is usually from 100 to 1800 kg/m3, preferably from 200 to 1200 kg/m3, particularly preferably from 300 to 1000 kg/m3.
Still another embodiment of the foam [I] is a rigid polyurethane foam [Ic] produced by forming a syntactic foam without using as auxiliaries (C) a blowing agent (C1) but using a hollow microsphere (C24), a dehydrating agent (C25), and as needed an inorganic powder (C23) as additives (C2).
The density of the foam [Ic] is usually from 100 to 1800 kg/m8, preferably from 200 to 1200 kg/m3, particularly preferably from 300 to 1000 kg/m3.
The rigid polyurethane foams [Ib] and [Ic] have advantages in that they are of light weight and have an even density distribution, and exhibit a fine surface when cut, and that reduction in the mechanical properties is small when their density is decreased.
In the foams [Ib] and [Ic], the inorganic powder (C23) and hollow microsphere (C24) are used as fillers. The inorganic powder is useful to increase the dimensional stability and material strength of the foam and to improve the flame resistance. The hollow microsphere is useful for lightening the weight or improving the processability of the molded product. Therefore, the amounts should be chosen depending on the use of the foam. For example, to improve the strength or dimensional stability of the foam, the amount of the inorganic powder may be increased. And to obtain a molded product that has a low density and is easy to cut, the amount of the hollow microsphere may be increased. The amount of the filler comprising the inorganic powder (C23) and hollow microsphere (C24) is usually from 2 to 60%, particularly preferably from 5 to 40% based on the total mass of the foam-forming composition. When the amount of the filler is not less than 2%, the bubbles generated in the mechanical froth foaming method are sufficiently maintained. When the amount of the filler is not more than 50%, the viscosity of the foam-forming composition does not become too high, so that production become easy.
In the foams [Ib] and [Ic], because the dehydrating agent (C25) is added to prevent blowing caused by moisture in the foam-forming composition, e.g. moisture in the fillers, during the urethanation reaction, its amount should be adjusted depending on the content of the moisture in the composition. It is also necessary to increase the amount of the dehydrating agent (C25) when the amount of the fillers is large. The amount of the dehydrating agent (C25) is usually from 0.5 to 8%, preferably from 0.8 to 6% based on the total mass of the foam-forming composition. When the amount of the dehydrating agent is not less than 0.5%, blowing is not caused by the absorbed moisture during the curing reaction, so that the obtained molded product exhibits a fine texture. Furthermore, when the amount of the dehydrating agents is not more than 8%, the molded product has good cutting workability.
In the foams [Ib] and [Ic], a dust-scattering reducer (C29) may be optionally added. The (C29) reduces the amount of the dust scattering when the molded product is cut. There is a tendency that the amount of the scattering dust increases as the density of the molded product decreases. Therefore, when the molded product has a low density, it is desirable that the (C29) is contained in a relatively large amount. The amount of the (C29) is usually from 3 to 30%, preferably from 5 to 20% based on the total mass of the foam-forming composition. When the amount of the (C29) is not less than 3%, the amount of the scattering dust decreases sufficiently. When the amount is not more than 30%, hardness and heat resistance of the molded product are not affected.
The foams [Ib] and [Ic] can be processed by cutting into desired shapes to produce cut moldings. The methods of the cutting include hand working using chisel, saw, plane or the like, and machine working using a CNC machine or the like.
The foams [Ia] to [Ic] may be rigid polyurethane foams that further contain staple fiber (C26) as an additive (C2). By using the staple fiber (C26), a rigid foam with high bending strength and high bending modulus can be obtained.
Particularly, because in the present invention the component (A) contains the compound (A1) and as needed the compound (A0), which reduce the viscosity of the composition, a staple fiber-reinforced foam having stronger mechanical strength may be produced by increasing the content of the staple fiber than in a conventional case. For example, when producing a mechanical froth foam [Ib], even if the amount of the staple fiber used in the composition is increased, the viscosity of the composition does not become as high as in a conventional case. Thus, mechanical stirring can be conducted sufficiently, so that inert gas is uniformly dispersed. Therefore, the obtained foam has high mechanical strength. Accordingly, a mechanical froth foam that can be applied to repeated uses such as materials of molds or to uses subject to a bending stress can be provided. When the foam is reinforced with staple fiber, the amount of the staple fiber (C26) is usually not more than 50 mass %, preferably from 10 to 50 mass %, particularly preferably from 20 to 40 mass % based on the total mass of the foam-forming composition. When the amount of the (C26) is not less than 10 mass %, its effect of reinforcing the resin is increased. When the amount is not more than 50 mass %, defects are not generated in the foam and a homogeneous foam can be obtained. Furthermore, when the foams [Ib] and [Ic] are reinforced with staple fiber, in order not to make the viscosity of the composition too high, the total amount of the staple fiber (C26), inorganic powder (C23), and hollow microsphere (C24) is usually not more than 60 mass %, preferably from 10 to 60 mass %, particularly from 20 to 50 mass % based on the total mass of the foam-forming composition. When the staple fiber (C26) is contained in the foams [Ib] and [Ic] as their components, staple fiber-reinforced rigid polyurethane foams, which have an even density distribution, which are of light weight and excellent in dimensional stability, and which exhibit fine surfaces when cut, and have high bending strength and high bending modulus, can be obtained.
Because the rigid polyurethane foam [I] has high strength, good thermal insulation and flame resistance, and particularly excellent dimensional stability, it can be used in a wide range of applications utilizing these characteristics. The uses of the rigid polyurethane foam [I] include refrigerators, freezers, thermal insulators for construction etc., shock-absorbing materials, synthetic woods (including for structural materials, materials for models, etc.), and the like.
Another embodiment of the polyurethane foam [1] of the present invention is a flexible polyurethane foam [II] that has a density of 10 to 500 kg/m3 and in which the component (A) satisfies the requirement that the M value expressed by the above formula (2) is at least 500.
The M value of the component (A) used in the foam [II] is preferably at least 800, more preferably at least 1,000, particularly preferably from 1,100 to 15,000. If the M value is less than 500, the flexibility becomes inadequate as a flexible foam. Furthermore, the density of the foam [II] is preferably from 15 to 200 kg/m3, particularly preferably from 20 to 100 kg/m3.
The value (on the average) of the active hydrogen-containing groups (hydroxyl value in the case of polyols) in the compound (A2) used in the foam [II] as needed is preferably from 4 to 200, more preferably from 10 to 150, particularly preferably from 15 to 120. When the value (on the average) of the active hydrogen-containing groups is within the above-mentioned range, a foam that has flexibility and in which the compression set is small enough can be obtained. Moreover, those preferable as the compound (A2) are the same as in the case of the foam [I].
One embodiment of the flexible polyurethane foam [II] is a flexible polyurethane foam that is formed using as auxiliaries (C) a blowing agent (C1) and as needed a foam stabilizer (C21) and/or an urethanation catalyst (C22) as additives (C2). Moreover, by further using inorganic powder (C23) and/or inorganic staple fiber (C261) as additives (C2), a flame-resistant flexible polyurethane foam can be obtained. The amounts of the (C23) and/or the (C261) used are the same as in the case of the above-mentioned foam [Ia].
The flexible polyurethane foam [II] is advantageous because it has good hardness so that its density may be lowered, and also it has small compression set. Therefore, it can be used in a wide variety of applications utilizing these characteristics. The flexible polyurethane foam [II] can be used as a cushioning material, shock-absorbing material, sound insulating/absorbing material, etc.
One example of the method for producing the polyurethane foam [Ia] by blowing with a blowing agent according to the present invention is as follows: First, a component (A), a blowing agent (C1), and as needed at least one additive (C2) are mixed in predetermined amounts. Then, using a polyurethane foaming machine or an agitator, the mixture is mixed with an organic polyisocyanate (B) rapidly. The obtained mixture solution (a foam base solution) is poured into a mold. After curing for a predetermined period, it is removed from the mold to obtain a polyurethane foam.
Furthermore, a polyurethane foam can be obtained by spray foaming or continuous foaming. Moreover, in a prepolymer method, the viscosity of the foam base solution in which individual components are mixed becomes high in the urethanation reaction. Therefore, a one shot process is preferably employed.
Moreover, the NCO index (equivalent number of isocyanate group per one equivalent of active hydrogen-containing groupxc3x97100) when producing the foam [Ia] is preferably from 40 to 500, particularly preferably from 60 to 250. If the NCO index is less than 40, the calorific value become low during the blowing. Thus, the expansion ratio may become small, the mechanical strength of the foam may be decreased, or the dimensional stability of the foam may be deteriorated. On the other hand, if the NCO index is more than 500, the foam may become brittle. Moreover, in a common process of forming a polyurethane foam, only the compound (A2) is employed as the polyol component, and the NCO index is usually at least 80. This is because, if the NCO index is decreased, mechanical strength is reduced, or dimensional stability is deteriorated. In the process of the present invention, however, because of the use of the self-polymerizable compound (A1), even when the NCO index is small, the crosslinking density becomes higher than in common urethane foams, and the decrease in the mechanical strength of the foam is small. Thus, even when only water is used as a blowing agent, if the NCO index is decreased, the amount of the organic isocyanate with respect to the polyol does not become large, so that a mixing deficiency is unlikely to occur during the blowing.
One example of the process for forming the mechanical froth foam [Ib] or syntactic foam [Ic] of the present invention is as follows: A foam-forming composition is usually produced by preparing two components separately, i.e. a component comprising the component (A) (hereinafter referred to as an active hydrogen component in the description of this process) and a component comprising the organic polyisocyanate (B) (hereinafter referred to as the NCO component in the description of this process). The active hydrogen component and the NCO component are prepared by mixing respective raw materials using a mixing vessel having a mixing blade such as of a propeller or paddle type, or using a planetary mixer, Hobart mixer, or the like. In the foams [Ib] and [Ic], fillers such as inorganic powder and hollow microsphere, dehydrating agents, dust-scattering reducers, foam stabilizers, urethanation catalysts, and the like are usually contained in the active hydrogen component, but they also may be contained in the NCO component. Particularly, when a large amount of fillers is contained, it is preferable that a portion of the fillers is contained in the NCO component. In such a case, by adding a dehydrating agent in the NCO component depending on the content of the fillers in the NCO component, deterioration with age (increased viscosity) of the NCO component can be prevented. Materials such as colorants or catalysts that are used in small amounts may be added preliminarily to the active hydrogen component, but they also may be added into the mixing machine at the same time when the active hydrogen component and the NCO component are mixed and molded through curing. The foams [Ib] and [Ic] are obtained by causing reaction in a composition comprising the active hydrogen component and the NCO component to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane in the absence of a blowing agent.
Furthermore, when producing the foams [Ib] and [Ic], the NCO index is preferably from 40 to 500, more preferably from 60 to 250, particularly preferably from 85 to 120. If the NCO index is less than 40, the mechanical strength of the foams may be decreased, or the coefficient of linear expansion may be increased. On the other hand, if the NCO index is more than 500, the foams may become hard and brittle.
The process for producing the mechanical froth foam [Ib] in which an inert gas is mixed and the process for producing the syntactic foam [Ic] in which an inert gas is not mixed according to the present invention are, for example, the procedures as follows, respectively.
In the process in which an inert gas is mixed:
(1) An active hydrogen component and a NCO component are prepared according to the above-mentioned processes.
(2) The active hydrogen component, the NCO component, and an inert gas are mixed uniformly in a certain ratio, and the mixture liquid is poured into a mold.
(3) After curing the mixture liquid in the mold, it is removed from the mold to obtain a mechanical froth foam [Ib].
In this process, it is preferable to use, for example, a mechanical froth method, i.e. a method in which a mixer with a high shearing force such as an Oakes mixer is used, to mix the active hydrogen component, the NCO component, and the inert gas uniformly. The mechanical froth method is suitable for continuously mixing a gas into a liquid ingredient.
Examples of the inert gas mixed are those that will not react with the active hydrogen component or with the NCO component, and that are not in a liquid state under the atmospheric pressure at a temperature of xe2x88x9230xc2x0 C. Preferable are air, nitrogen, and carbon dioxide gas. The amount of the inert gas mixed is usually from 10 to 70%, preferably from 20 to 60% based on the total volume of the inert gas and the entire composition.
In the process in which an inert gas is not mixed:
(1) An active hydrogen component and a NCO component are prepared according to the above-mentioned processes.
(2) The active hydrogen component and the NCO component are mixed uniformly in a certain ratio, and the mixture liquid is poured into a mold.
(3) Defoaming under a reduced pressure is performed, and the bubbles contained in the mixture liquid in the mold are removed.
(4) After curing the mixture liquid in the mold, it is removed from the mold to obtain a syntactic foam [Ic].
In this process, the mixing is performed by stirring with a mixing blade such as a propeller type, flat blade type, curved blade type, Pfaudler type, paddle type, or the like in a mixing vessel, or by using a mixing machine such as a screw type, kneader type, universal type, etc. Usually, a mixing machine of either screw or kneader type is employed.
The polyurethane foam [2] of the present invention is an elastic polyurethane foam obtained by reacting an addition-polymerizable active hydrogen component (Axe2x80x2) mentioned below with an organic polyisocyanate (B) in the presence or absence of at least one auxiliary (C) selected from the group consisting of blowing agents (C1) and additives (C2) to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane.
Addition-polymerizable active hydrogen component (Axe2x80x2): an addition-polymerizable active hydrogen component, which comprises an active hydrogen-containing group (w) and an addition-polymerizable functional group (x), and which is selected from the (A31), (A32), and (A33) below; wherein the reaction rate constant K1 between the active hydrogen-containing group (w) and an isocyanate group (z) at 120xc2x0 C is not more than 1 (liter/mol/sec); polymerization reaction rate constant K2 of the addition-polymerizable functional group (x) is not less than 10 (liter/mol/sec); and K2/K1 is not less than 100.
(A31): an addition-polymerizable active hydrogen compound that has an active hydrogen-containing group (w) and an addition-polymerizable functional group (x), and which may have a cyclic group (y) reactive with the group (w).
(A32): an active hydrogen compound (A321) having at least three groups (w) or having the groups (w) and (y), and an addition-polymerizable compound (A322) having the groups (x) and (y), used in combination.
(A33): the compound (A31), and the compound (A321) and/or the compound (A322), used in combination.
In producing the foam [2] of the present invention, the addition polymerization of the addition-polymerizable functional group (x) and the urethanation reaction between the isocyanate group in the organic polyisocyanate (B) and the active hydrogen-containing group (w) are carried out in the same reaction system. Moreover, in the present invention, it is understood that to polymerize the addition-polymerizable functional group and simultaneously form a polyurethane means that the polymerization of the addition-polymerizable functional group and the polyurethane-forming reaction are carried out simultaneously at least partially during the reaction period. In order to improve the mechanical properties with increased crosslinking density, it is preferable that the other reaction is initiated before a resin is formed through curing in one reaction, so that the two reactions are carried out at the same time.
The active hydrogen-containing group (w) used in the foam [2] of the present invention has a reaction rate constant K1 between the group (w) and isocyanate group of not more than 1 (liter/mol/sec) at 120xc2x0 C. Examples of such an active hydrogen-containing group (w) are hydroxyl, mercapto, carboxyl, primary amino, and secondary amino groups, and the like. Preferable among these are hydroxyl or mercapto group, particularly preferably hydroxyl group.
As the addition-polymerizable functional group (x) used in the present invention, an addition-polymerizable functional group which has a polymerization reaction rate constant K2 of not less than 10 (liter/mol/sec) at 120xc2x0 C., K2/K1 being not less than 100, may be employed. Examples of such an addition-polymerizable functional group (x) are radical-polymerizable groups, cationic-polymerizable groups, and anionic-polymerizable groups. Preferable among these are radical-polymerizable groups.
Examples of the radical-polymerizable groups include acryloyl, methacryloyl, vinyl ester, vinylbenzyl, vinylphenyl, vinylidene, and allyl ether groups, and the like. Preferable among these are acryloyl or methacryloyl group. Examples of the cationic-polymerizable groups include vinyl ether group, propenyl ether group, and the like. Examples of the anionic-polymerizable groups include vinylcarboxyl group, cyanoacryloyl group, and the like. Examples of the cyclic group (y) reactive with the group (w) include epoxy group, anhydrous maleyl group, and the like. Preferable among these is an epoxy group.
The number of the active hydrogen-containing groups (w) in the above-mentioned addition-polymerizable active hydrogen compound (A31) is usually from 1 to 10, preferably from 2 to 5. Furthermore, the number of the addition-polymerizable functional groups (x) in the compound (A31) is usually from 1 to 10, preferably from 1 to 5. Furthermore, the number of the cyclic groups (y) in the compound (A31) is usually 0 or from 1 to 5, preferably from 0 to 2.
Examples of a compound (A311) having an active hydrogen-containing group (w) and addition-polymerizable functional group (x) in one molecule among the compounds (A31) include the same compounds as the compound (A1) used in the above-mentioned foam [1].
Examples of a compound (A312) having the groups (w), (x), and (y) in one molecule among the compounds (A31) include partially glycidyl-etherified partial esters of unsaturated carboxylic acids with polyols. Examples of the partial esters of unsaturated carboxylic acids with polyols include the same compounds as the compound (A1/1) used in the above-mentioned foam [1]. The partially glycidyl-etherified materials mentioned above as examples of the compound (A312) are obtained by partial esterification and partial glycidyl-etherification of polyols, which are performed either sequentially or simultaneously, using unsaturated carboxylic acids and epichlorohydrin.
It is preferable that the relationship between the (number average) molecular weight W and the total number F of the groups (w), (x) and (y) in one molecule is W/F greater than -1000 in the compound (A31), so that the elasticity of the urethane foam is easily maintained when the amount of the (A31) used is increased. It is particularly preferable that W/F is from 1200 to 5000.
A compound (A321) is either a compound (A321/0) having at least three groups (w) and not having the group (y), or an active hydrogen compound having the groups (w) and (y). The number of the group (w) in the (A321/0) is usually from 3 to 10, preferably from 3 to 6. Moreover, in the compounds (A321) other than the (A321/0), the number of the group (w) is usually from 1 to 10, preferably from 2 to 6, and the number of the group (y) is usually from 1 to 5, preferably from 1 to 2. The group (y) reacts with the group (w) contained in the compound (A31) or (A32) rapidly to form a bond therebetween as well as to form a new active hydrogen-containing group (wxe2x80x2). Therefore, in the case of the active hydrogen compound having the groups (w) and (y), the number of the group (w) may be from 1 to 10 but in the case of the compound (A321/0) not having the group (y), it is necessary that the number of the group (w) is from 3 to 10.
The compound (A321/0) among the compounds (A321) may be at least one selected from known polyether polyols, polyester polyols, polyhydric alcohols, and amines [polyamines and alkanolamines] commonly used in polyurethane foams as listed above in the description of the foam [1], in which the number of the active hydrogen-containing groups is within the above-mentioned range.
Examples of an active hydrogen compound having the groups (w) and (y) among the compounds (A321) include the (A321/1) to (A321/4) as follows:
(A321/1) Partially glycidyl-etherified polyols
(A321/2) Partially glycidyl-thioetherified polythiols
(A321/3) Epoxides having hydroxyl groups
(A321/4) Substituted maleic anhydrides having hydroxyl groups
The compounds (A321/1) can be obtained by reacting the above-mentioned polyols with compounds containing epoxy groups such as glycidol or epichlorohydrin.
The compounds (A321/2) can be obtained by reacting the above-mentioned polythiols with compounds containing epoxy groups such as glycidol or epichlorohydrin.
Examples of the compounds (A321/3) include glycidol and the like.
Examples of the compounds (A321/4) include hydroxyethyl maleic anhydride and the like.
In the present invention, a vinyl polymer (F) may be dispersed in the compound (A321) as needed. The polymer (F) may be dispersed in the compound (A321) after it is polymerized, but preferably it is dispersed and stabilized by polymerizing a vinyl-based monomer (f) in the (A321). Examples of the monomer (i) include acrylonitrile, styrene, vinylidene chloride, alkyl (meth)acrylate, and the like. Preferable among these are acrylonitrile and styrene. The amount of the polymer (F) is usually from 5 to 50 mass parts, preferably from 15 to 45 mass parts per 100 mass parts of the compound (A321).
The compound (A322) is an addition-polymerizable compound having an addition-polymerizable functional group (x) and a cyclic group (y). The number of the group (x) in the compound (A322) is usually from 1 to 10, preferably from 1 to 5. Furthermore, the number of the cyclic group (y) in the compound (A322) is usually from 1 to 5, preferably from 1 to 2.
Examples of the compound (A322) include glycidyl acrylate, glycidyl methacrylate, maleic anhydride, and the like. The groups (y) in the compound (A322) are suitable for increasing the reaction rate because they react with the groups (w) contained in the compound (A31) or (A32) rapidly to form a bond therebetween as well as to form a new active hydrogen-containing group (wxe2x80x2). However, because the group (wxe2x80x2) has a large steric hindrance, unreacted active hydrogen-containing groups may remain, or its ring may open independently by reacting with water due to the effect of an amine catalyst, which may be used as a catalyst of urethanation reaction, and deteriorates the properties of the foam without contributing to the crosslinking. Therefore, it is preferable that the addition-polymerizable active hydrogen component (Axe2x80x2) comprises the addition-polymerizable active hydrogen compound (A31) or comprises the compound (A31) and the active hydrogen compound (A321).
When the component (Axe2x80x2) comprises the above-mentioned (A31) or (A33), it is preferable that the (A31) is from 1 to 100 mass %, the (A321) is from 0 to 99 mass %, and the (A322) is from 0 to 50 mass % based on the total mass of the (A31), (A321) and (A322). It is particularly preferable that the (A31) is from 5 to 100 mass %, the (A321) is from 0 to 95 mass %, and the (A322) is from 0 to 30 mass %.
When the component (Axe2x80x2) comprises the above-mentioned (A32), it is preferable that the (A321) is from 50 to 99 mass %, and the (A322) is from 1 to 50 mass % based on the total mass of the (A321) and (A322). It is particularly preferable that the (A321) is from 70 to 98 mass % and the (A322) is from 2 to 30 mass %.
In the present invention, an elastic urethane foam that is produced by reacting a component comprising the compound (A31) used as the component (Axe2x80x2) [including the case in which a compound other than the (A31) is also contained] and a polyisocyanate component as essential components has a Mxe2x80x2 value expressed by the formula below of usually at least 500, preferably at least 800, more preferably at least 1000, particularly preferably from 1,100 to 15,000:
Mxe2x80x2 value=Jxe2x80x2/(Kxe2x80x2+Lxe2x80x2xc3x972xe2x88x922) 
wherein Jxe2x80x2 denotes the (number average) molecular weight of the addition-polymerizable active hydrogen component comprising the compound (A31), Kxe2x80x2 denotes the (average) number of the group (w) per molecule, and Lxe2x80x2 denotes the (average) number of the group (x) per molecule.
If the Mxe2x80x2 value is less than 500, the flexibility of the elastic polyurethane foam is reduced.
Examples of the organic polyisocyanate (B) used in the foam [2] of the present invention include the same compounds as in the above-mentioned foam [1], and those preferable are also the same as in the above-mentioned foam [1].
When producing the foam [2] of the present invention, in the case of using a compound having a radical-polymerizable unsaturated group as the addition-polymerizable functional group, reaction can be carried out in the presence or absence of a radical-polymerization initiator or a chain transfer agent as in the process for producing the foam [1]. Also, the types of the radical-polymerization initiator or the chain transfer agent that may be employed, their amounts used, or those preferable are the same as in the process for producing the foam [1].
At least one selected from the group consisting of water, hydrogen atom-containing halogenated hydrocarbon, low boiling point hydrocarbon, and carbon dioxide may be used as a blowing agent as needed. In terms of preventing harmful effects to the earth environment and maintaining the working environment, water or carbon dioxide is preferably used. There has been a conventional problem that hardness is more difficult to develop when using carbon dioxide as a blowing agent than when using water. However, because hardness can be improved in the present invention, carbon dioxide also may be preferably employed as a blowing agent.
In the same way as in the process for producing the foam [1], urethanation catalysts and foam stabilizers may be used as needed, and the types and the amounts used thereof are also the same.
Furthermore, in the same way as in the foam [1], various known additives and auxiliaries, e.g. surfactants such as emulsifiers and foam stabilizers, age resistors such as antioxiants and ultraviolet ray absorbing agents, inorganic powders such as calcium carbonate and barium sulfate, staple fibers such as glass fiber, carbon fiber, and potassium titanate whisker, flame retardants, plasticizers, polymerization inhibitors, colorants, antibacterial agents, antifungal agent, and the like may be used as needed.
One example of the process for producing the polyurethane foam [2] of the present invention is as follows: First, an addition-polymerizable active hydrogen component (Axe2x80x2) is mixed with a blowing agent, foam stabilizer, catalyst, radical-polymerization initiator, and other additives in predetermined amounts as needed. Then, using a polyurethane foaming machine or an agitator, this mixture is admixed with an organic polyisocyanate (B) rapidly. The obtained mixture solution (foam base solution) is poured into a mold, and after curing for a predetermined period, it is removed from the mold to obtain a polyurethane foam. Furthermore, a polyurethane foam may be obtained by spray foaming or continuous foaming. Moreover, in a prepolymer method, the viscosity of the foam base solution in which individual components are mixed becomes high in the urethanation reaction. Therefore, a one shot process is preferably employed. Furthermore, the polyurethane foam also may be obtained by a mechanical froth method without using a blowing agent.
Moreover, the NCO index in the case of producing the foam [2] is preferably from 40 to 500, particularly preferably from 60 to 250. If the NCO index is less than 40, the expansion ratio may become small due to the small calorific value during the blowing, or the mechanical strength of the foam may be decreased. On the other hand, if the NCO index exceeds 500, the foam may become brittle.
The polyurethane foam [2] of the present invention can be used as a cushioning material, shock-absorbing material, sound insulating/absorbing material, etc.
The present invention will be further described by referring to the following non-limiting Examples and Comparative Examples.
In the following Examples and Comparative Examples, the xe2x80x9cpartxe2x80x9d means xe2x80x9cmass partxe2x80x9d unless specified otherwise.
Evaluations of the Polyurethane Foams [Ia] and [II]